Tips of acros problem

[jnewman]

I have some acros that have been great and have good growth but now all the sudden I am seeing the tips are turning white and then algae starts to grow on them which stops any growth over the areas. I am at a lose no pest to my knowledge and nothing new in tank. I buy from a place that treats and insures that pest are gone.
Here is my tank 125g with 2- 250w 14k bulbs new. Fish- fowlerii orange shoulder, 2 clown, 3 damsels & 2 striped gobies. CUC snails, pep shrimp & cleanner shrimp. Water para. - ca. 430-420, no2- 0, no3 - 0-5ppm, phos. - 0-1, mg -1350, dkh - 6, alk -2.06 & ph-8.3. My cal & dkh go up and down I dose so it has been hard to keep both steady.
Any sugestion woold be great

[29reef]

Your DKH Aka alkalinity should be around 9-12dkh and stable. This can cause problems with growth if it is lower than ideal or too high.

[ReefWreak]

As mentioned, in case you doubted him^^, it's your alkalinity :p Trust me. i've had the same problems, and tip recession is 99% of the time caused by alkalinity swings/changes/burns/etc.

[RockDocPro]

It does seem that your dkh/alk is low. Also, wide fluctuations in the Ca and alk can cause problems, even if the overall average is within normal limits. I recently had a mild alk overdose, and my dkh went from 8 to 11 within 24 hrs. I lost several corals over the next few days. Slow infusion of 2 part with a dosing pump might smooth out the peaks and valleys. Best of luck!