Adding Lime To Soil

I am wondering about adding lime to my soil -to acchieve a neutral PH- I believe the PH level in my soil is low -acidic-
I am wondering if i can/should add lime to correct this.
I am worried about salt build up, I used sh**ty MG ferts for the first few months cause that was all I had. I have just bought proper fetrts.
some of my plants are early in the bud stage and I am wondering if I can add lime on top of the soil. or if i have to mix it it. if so how deep do i need to go? (plants are in 3 gallon buckets)
-OR- does the lime need to be added in the very beginning of planting when i make my soil mixture? i heard this works for keeping the ph of the soil neutral
If I shouldn't use lime....than what should i use? This is concerning the PH level of my SOIL not my water. ..(I have ph up and down for the water) what should I do??

Also, my babies are growing slower than i had anticipated, the tempature at the tops of my plants is 92F+ degrees (can get up too 100F on hot days) I have a 1000 watt light . and a 500 cfm fan, (no ducting though, just keep the door open and the fan blowing in on them) fan is on 24 hours. This is all in a closet, as i live in the city and have no where else to grow. Q: is this too hot? the tops of the plants are about 8-12 inch from the light. I dont see any burns or anything, they are just growing really slow.
Thank you to any one who takes the time to respond to my question.

Yes, you can add lime to the top of your soil, both the pellet-type, and the powder. I always do it around week 2 of 12/12(around week 8, total). If you are having PH problems, and want it to be more effective, take a long piece of wire(like coathanger wire) and poke a bunch of deep holes in your soil, allowing the lime to fall down in, as you water. Works great, I've done it on more than one occasion.


And,....yes, your temps are too hot, which is why they're likely growing slowly. If you can't do anything about it, just make sure they have water, and the humidity is okay(around 50%), and that's about all you can do. Also, watch for hermies. It's been my experience that plants in excessive heat, tend to hermie from the stress. That's something I don't see mentioned on here very often, but is something I believe to be true.