Need help please

[420Harley420]

New to growing plants are 8 week old everything i found says over watered but i know for sure it's not they get watered once a week and it hasn't changed this is the first problem i had but I'm worried it might kill plants the leafs are droopy some curl under some curl over i have pics but I'm new to page and not sure yet how to post them they don't look good any help will be welcomed thank you also i have 4 plants and only 3 are affected

 

[Dan Ultra]

What are your temps and humidity like?

Looks either over watered or under watered. When you water them, do you check the weight of the pots first? You should only water when they feel light, and not let them stay light for very long. 1-2 days max