Are My Plants Dieing ? 1st timer needs advice

hi,
im new on here and its my 1st time growing, i have three plants at about 5 weeks old, i noticed little white spots on the leafs and did some research and found they was spider mites which after closer inspection i could see little brown crab like creatures, so i treated them which seems to have worked but the white spots remain.

for the past 2 weeks i havnt really seen much growth in my baby's, last week i started to notice yellow leaves and more and more came then i noticed a few had gone brown and holes in them ( see pics )

after checking today iv noticed the top new leafs are starting to curl up

what do you guys think ??

info: blue cheese strain
400watt light
30 liter size tubs
fan assisted
coco soil
canna part a and b food.
around 30- 32'c temp
tallest is 1.5 ft

since i got them at 1 week old iv been mixing 25ml of part A and B of the food with 10 liters of water, i got told yesterday i should be doing 25ml of each with 2 liers of water !!?

is this true ? maybe iv not been giving them enough food ??
alos when should i start to flower as they dont seem very big yet

any help much appreciated

looks super n bushy to me why do u think they r dying bc of yellow tips? ad slight amt of N... but looks fine, they even out
lower leaves tend to die off first

well yeh b'cos of the yellow leafs and alot of the tips av turned yellow/brown and they dont seem to be growing much now

Are you smoking near you're plants? I do not think your plants are looking that bad. Picture four looks like the leaf isn't getting enough light due to the leafs on top and that's fine, did you mist nute's on your plant when it was young because there's only leaf damage on the bottom

Hi mate. Im using coco coir and CANNA product's.

It looks to me that you maybe over feeding them. And the yellowing could be a nitrogen deficiency. The white spot's that appear on your leaves may be from thrip insect's which scratch and open the leaf to draw out the sap. But if you can get a microscope or magnifying glass and have a real good look at a bug, then go on to google and type in pest's on cannabis you should find exactly what you have and be able to treat it. If the spots are silvery white and irregular in shape then i would say you have a thrip infestation. At least get some washing up liquid and use this as a folar spray with ph6 water 1 tea spoon per liter. And if you can get some neem spray from your local B and Q or equivalent then do it and use it. Mist them just as the lights go out to avoid burning your leaves. And give them a small shot of nitrogen and they should become greener. If the leave tips are showing burn to the tip's, then a good thing to do would be to flush the pots with 3 x the amount of medium to stop any salt build up. Also if some of the lower fan leaves are turning yellow. Dont be too concerned about this. Your plants will naturally dismiss any old leaves that it cannot use. you can pull these of but dont pull top fan leave's of......

Hope this help's dan

thanks for the great advice lads! danthebull i dont think i have a pest problem as i had spider mites a few days ago and i sprayed the whole plant and killed those motherfu*kers ! and since posting this they are starting to look alot better i think iv been under feeding them all this time with only 50ml to 10litres of water when i should have been doing 50ml to 2 litres of water!