What kind of food are you using?
And how much do you feed them?
Also what kind of light & how close from the top of the plants is it?
Looks to me like nutrient problem.
that's what i was thinking too...i think that my better half put some more nutes in the mix...we're using the flora series...do you think flushing will help. oh...using a 400W MH. that particular plant is about a foot from the light...but is not under it at all.
First pic looks like the plant got to close to the light. The damaged tips seem to be on one side of the plant. The resin may not have formed yet depending on how long they have been in flower (you don't mention it). Are they bag seed? or do you know the strain? If you want real help you need to give more info. PH, light, strain, age, flowering time, ect.
Your light is too close try and keep it 2 to 3ft above.
PH should be around 6.5 but 6 is not going to harm it.
And what strain is it?
Looks like heat stress from light being too close.
And by the color of your plant I think nutrients should be adjusted too
Raise light up & post new pics in a week.