Learning how to tune is part of the nitro experience, bringing it to a professional every time you need somebody to man the screwdriver is ludicrous.

To look at the clutch, you have to remove the clutch bell. The spring may have lost temper from heat, or simply came unhooked.

The hsn controls all the fuel in, changes in hsn have an effect on the lsn.
Changes in the lsn will have an effect on the idle.
Hsn adjustments can usually be done independently of other adjustments.
Lsn adjustments usually have to have a corresponding adjustment to correct the idle.
Make small adjustments(like 1/12 of a turn), and allow the engine to get used to the new setting.