4 plants doing great, one doing crap?

All plants are under the same conditions, four of them are booming, one is 1/3 the size of the others and all the leaves on it are limp. I've tried to move it around my growing space to see if it will improve. Does anyone know what the problem could be? TY in advance.

Forest Gump of the bunch. it'll catch up, maybe.

3 diamonds, 1 lump of coal........it happens

Throw that one outside in the sun and leave her there. She'll thank you for it.

It may not like the same things the others r thriving under... Like, u may try to step back the watering on that one... But, if u put it outside, and u dont hide it well enuff, then u r risking em all, because if u r in a uncool area, then u dont wanna give any hints(like a plant outside) that u r growing... And even if u r in a cool area, u still may not wanna rouse anyones prying eyes... Id try to tweek the nutes after reading a bit in a good book by Ed Rosenthal, and mabye tweek the watering, and check for pH, and other things before I put is outside if I were u...