Is there a way to scan for stocks in weak sectors?

I think you would want to find the weakest sectors in a separate scan.

First you would have to have some measure of weakness, maybe per cent change over three months.

Then you would need a list that includes all the sector SPDR ETFs, or other kind of sector indexes. Your scan to find the weakest sectors would be a simple 'rank by' statement using your choice of strength/weakness measure.

For instance
// begin scan

// rank sectors by 3 month per cent change

[favorites list is 133] // Sector SPDRs daily (substitute your list)
rank by PctChange(60,close)

// end of scan

Then add the bottom 3 results to the scan you have above with an "OR" statement. Select the sectors from the "Sectors and Indexes" drop down, and edit
// Start scan

// you don't need "country is US" if you name the sectors

[ // begin OR statment

[group is HealthCareSector]
OR
[group is TechnologySector]
OR
[group is RealEstateSector]

] // end OR statement

and [macd line(12,26,9) <= macd signal(12,26,9)]
and [yesterdays macd line(12,26,9) > yesterdays macd signal(12,26,9)]

... etc.

At the top, after the sectors "OR" statement, you may want to add some other ticker properties to limit the results, e.g. volume and/or market cap, like

and [market cap > 1000]
and [sma(20, volume) > 1000000]

or whatever you are interested in.