You are feeding superthrive way too often. It's not that you're not following the directions, as 1 drop per gallon is correct. But you are doing this every other day, when in reality you should be doing this once a week max, maybe only once every two weeks.
Your babies are young and need very little. I know it's easy to want to try and do too much and give them more than they need thinking you are going to speed growth or increase yield, but don't buy into everything the labels say & sound like, you cannot force a plant to grow faster than physically possible. Patience!
What you NEED to do in order to get your plants on track and prevent the curling, is to do a SOIL FLUSH
This consists of making sure the bottom of your cups have proper holes or slits in the bottom so that they can drain properly
Begin running them under a faucet and flushing the soil well
Continue doing this for 5-15 min
When you first do this, you'll notice the water coming out of the bottom (runoff) is most likely dark, brown, amber colored. This is nutrient concentrated soil. As you flush, it will start to become more clear. This is a sign that your soil is starting to flush and go back to neutral. Use this as a sign as to whether it needs 5 or 15 min of on/off flushing.
If you have a TDS meter, this helps greatly, as you can gather the runoff from the beg of the flush and see what comes out. This will be what your current soil PPM is at. Flush, then test the PPM when it comes out clear. When the PPM is close to what the water PPM is prior to going thru the soil, you know that you have successfully removed any/all excess nutrients. If you don't have this meter, don't worry, just make sure you get it all out.
After this flush, you want to lay off water for a few days as your plants aren't feeding much and you certainly don't want to drown them and create a new problem. Consider after this flush transplanting them into new/bigger containers. To increase drainage, make sure your soil mix has ample quantities of perlite. This will help a lot and also allows extra air pockets for roots to breathe.
Hope this helps homes!
+++ rep??? What?
