Butchie,
Your cabinet is very similar to mine. My walls are flat white in fact everything is white so putting mylar will help but not significantly, as you saw from my grow white works fine, Also I got my plants to grow so many collas by doing extensive LST. They were never more than 8" tall for 5 weeks.
Also I use MG moisture control I saw you used that in the past and had good luck with it, now you are having difficulty with the new soil mix, so go back to what you know works if you can.

Then for starting cloans I recomed using rockwool cubes, they hold water a lot better and are much neater. Then for a carbon filter I use 2 - 4'' can filters
Have you seen HTGsupply.com it is one stop shopping for your needs at great prices.

Hope this helps you.
Jerry Garcia 2007 Reviewed by Jerry Garcia 2007 on . My 1st/2nd/3rd Grow Log Hey all - I have been quite innept at starting my own grow log, piggy-backing on others logs so I could post my pics, now that I can officially sart my own thread/with pics, I thought I would!! Lets start from the beginning... I was given 2 plants that were VERY malnourished and lacking in every department, so I took them on as a project (keep in mind, I hadnt attempted a grow in 13 years). So I read and read and read. And this is what has taken place over the last 3.5 months +/-...... Rating: 5