Help. I have 4 Green Giants that I planted 2 years ago as a privacy screen. Now all are between 8-10 ft tall. Were doing great last year. Now it's spring and I notice that for all the trees, the bottom half has become sparse and tips are brown. Top 50% looks good, still green, not sparse. I want the trees for privacy, so the sparseness at bottom half is not what I wanted. Want them to be fuller and wider.

Facts:

- NJ zone 6

- New growth upwards, lots of cones on bottom half

- planted in full sun

- Last year, I put slow release fertilizer stakes in ground

- have mulch from trunk to 1 foot diameter around trees, no mulch at trunk.

- Grass beyond the 1 ft diameter of mulch.

What do I do to get the trees to fill in?

Is the grass still too close to the trees? Should I use roundup to get rid of grass for a larger diameter around the tree?

Do I prune the brown tips? Do I leave it?

Do the trees need more water? Fertilizer?