HELP me save this poor great white shark! 17 days old! MACRO PIKS

So my great white shark seems to be alot slower than my other plants.. i am treating all 6 plants the same but shes the only one that is stunted.. leaves curling down and the tips seem o be turning a wierd colour. The only other plant that is showing this sort of problem is my white rhino which is alot larger but yet the leaves are curling down also with the outside of the leaves looking very sharp.

Temps never raise above 82 and very rarely even reaches that temp, Normally its is like 76-78 and 65 at night. I started fertilizing with bio bizz root juice 2ml per litre and only feed on every 3rd watering so im kinda sure it cannot be nute burn.. basically i just want to diagnose and and find a way to fix them... First 2 piks are great white shark and the last 2 are white rhino. Thanks

a pH imbalance will do that do the leaves. and do NOT fertilize anymore! they need a bit of nutes after they about a foot tall, but you really dont need much. When you are fertalizing them, you also want to flush them with straight water every week too so that no salts build up. For example, if they arent using much phosphorus, then it will sit in the soil and build up and that will change your pH and eventually cause burning

the yellowing of the lower leaves looks to me like over watering. Are you letting the soil dry completely before watering again?

Im pretty sure, ive been watering once every couple of days... Could it have anything to do with ph?

Ph is wayyyyy overrated. Unless ur hydro? I dont check mine,ever! Its a defiency. Up that plants nute solution by a 1/4. The bad growth will remain, but the new growth will be fine..

But it could be overwatered..

That soil looks really damp and even soggy. Lay off the watering and nutes for a while and see what happens.