Yellowing tips on lower leaves what’s my likely problem

[KOTN]

I’m so new to this indoor grow stuff, just watering with tap water. Is this perhaps a ph problem, only been feeding it seaweed fish once a week. Plant is only 5 days since I flipped to flower.

 

[Shayne010944]

Looks like cal mag deficiency. I could be wrong but that’s what mine looked like

 

[Jungle666]

Foliar spray it with Epsom salts should help