Slight browning on the leaf

Just use less. Give a pure pH watering and then on the next one start feeding less of each but don't cut any of them out. If your in soil you need to give pure pH water between feedings to prevent salt and nutrient buildup. You should only feed every time in coco.

Its only happened on the older growth so should i just use normal water for now and see what happens. I use a root stim and mag cal shall i stop using that too?

Either overwatering or nutrient burn. Both will show that sign. I'm running a DWC hydroponic bucket experimental run with a Platinum OG autoflower, I gave it an excessively high dose of potassium and it has those same marks on all lower leaves. I was overfeeding Armor Si to see if it would push the plant to grow larger then advertising

Looks like nutrient burn

It’s hard under the blurple but looks like a lil bit of nute burn. Is it on old or new growth? If only on old don’t worry too much.