pH run off crazy low, coming out 2.7 when I water at 6.5?!

Growing in 2gallon plastic pot
Using Coast of Maine soil
Using Botanicare cal-mag, Veg and Flowering nutrients
50w led grow light

So I'm having a slight deficiency going into week 3 of flower, think I just under fed going into the transition from veg to flower and it's starting to show now. So today I gave her another good dose of flowering nutrients and figured I check the pH runoff to make sure that was in check... Well it came out reading 2.7-2.8 which I have never had it get so drastically low before. I water between 6.4-6.6 every time I water and my ppms coming out are in the 900-1000 range so I really don't know why my run off is so low. Any ideas?

Running to runoff?? If not , salt build up.
Did you transplant to bigger pots before flip?

Yes I water to about 20% runoff, and they are autos so I didn't want to transplant and figured she would be fine since she wasn't all that big before it switched

SBBCal said:

Running to runoff?? If not , salt build up.
Did you transplant to bigger pots before flip?

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Replied but for some reason it didn't attach to your initial response

Autooosss... that idk . But soil is soil. If they’ve been in those pots and same soil for awhile they prob have something root related. Either buildup/lockout or root rot. Have you tried any Teas?? Build up that soil again
- and I just noticed it said 50w light, shit ain’t going to cut it in flower.